During operation of an internal combustion engine, a fraction of combustion gases can flow out of the combustion cylinder and into the crankcase of the engine. These gases are often called “blowby” gases. Typically, the blowby gases are routed out of the crankcase via a CV system. The CV system may pass the blowby gases through a coalescer (i.e., a coalescing filter element) to remove a majority of the aerosols and oils contained in the blowby gases. The coalescer may be a rotating coalescer or a stationary coalescer. The filtered blowby gases are then either vented to the ambient (in open CV systems) or routed back to the air intake for the internal combustion engine for further combustion (in closed CV systems).
In rotating coalescer and non-rotating coalescer CV systems, there is a need to detect a missing filter element. If the CV system is an emissions controlling device, as is the case in open CV systems, then there may be a jurisdictional requirement to detect if the installed (or missing) coalescer does not meet emissions standards. For closed CV systems, such detection and prevention systems are typically deployed at the requests of customers to detect a missing or improper element.
In some rotating coalescer arrangements, these detection and prevention needs are met with the inclusion of a revolution per minute (“RPM”) sensor that communicates with the internal combustion engine's engine control module (“ECM”). However, not all ECMs include an available input/output port that can accept input from an RPM sensor. Further, RPM sensors can be relatively expensive components.
In some static coalescer arrangements, detection and prevention needs are met by using the existing crankcase pressure connectors. Static coalescers typically have a large pressure drop across the media of the static coalescer. Accordingly, it is possible to detect a missing filter by comparing actual pressure drop values with expected pressure drop values across the CV system as well as comparing differences of crankcase pressure based on the engine duty cycle. However, this form of detection is not possible or is very difficult for rotating coalescers, because most rotating coalescer arrangements have minimal associated pressure drop (e.g., close to zero inches of water) across the element. Accordingly, a missing element situation may not be detected by a crankcase pressure sensor.